1. Field of the Invention
The present invention relates to an antenna for use in an implantable medical device. More specifically, the present invention relates to an antenna insulation for an external antenna of an implantable medical device.
2. Discussion of Related Art
Some implantable medical devices communicate with an external device via radio frequency (RF) telemetry. To achieve this, the implantable medical device requires an antenna to communicate with the external device.
U.S. Pat. No. 6,456,256 disclosed placing the antenna on the exterior of the implant housing to permit far-field radiation. The antenna is disclosed as being embedded in an antenna compartment that is made of dielectric material. The antenna is disclosed as not being welded to a feedthrough, but simply is routed from the transmitting and receiving electronic circuitry within the housing through the feedthrough to the dielectric compartment with no connections.
An external control unit has a radio frequency emitter that can emit a carrier frequency f. When manufacturing the implantable medical device and external control unit associated therewith, both the external control unit antenna and the antenna of the implantable medical device are tuned at a carrier frequency f. However, once in use, any contact of bodily fluid with the antenna wire of the implantable device will generate stray electrical capacitances and detune the antenna thereby decreasing telemetry performance. Of course, once an implantable medical device is implanted, the only way to correct the detuning, is to remove the implant, which is clearly not desired.
Thus, it is an object of the present invention to provide an implantable medical device that will ensure that fluids will not come into contact with the antenna and therefore the tuning of the antenna will remain constant.